How do I keep java XMLEconder from using so much memory when writing a List?

I have serializable relational javabean BO's in an ArrayList (boList) that I want to write to XML using XMLEncoder or some other standard method.

Using:

XMLEncoder encoder = new XMLEncoder(new BufferedOutputStream(
   new FileOutputStream("C:/tmp/test.xml")));

encoder.writeObject(boList);
encoder.close();

I run out of memory. If, however, I do this:

for(BO bo : boList)
{
    encoder.writeObject(bo);
    encoder.flush();
}
encoder.close();

It runs perfectly using very little memory. I know the flush() writes generated xml to the file and releases referenced memory which makes sense. I suspect when writing the boList the XMLEncoder it is trying to generate all XML before writing for which there is not enough memory.

I need to be able to write the boList to XML as it will be a field in a parent BO which will be written to XML. How do I get this to behave with the list as in the case where I call "writeObject" on each separate object? Is there an alternative to XMLEncoder that will accomplish this which is as straightforward to use? This must be accomplished using standard JRE/Java 6 functionality with no third party libraries. Thanks!